This application proposes neurophysiological studies to determine the role of sleep in the development and plasticity of the mammalian visual cortex. Our previous research has demonstrated a role for sleep in the plasticity elicited by monocular deprivation (MD) during the critical period for visual development in the cat. These findings suggest an important role for sleep in the developing brain and have important implications for our understanding of cortical plasticity, learning and memory, and the function of sleep. In addition to providing insights into these areas of study, the proposed studies should provide important information regarding the role of sleep in human neural development, and the long-term consequences of sleep loss on the developing brain. The overall goal of the proposed studies is to determine the contribution of rapid-eye-movement (REM) and nonREM sleep to two forms of developmental plasticity in visual cortex. Short periods of MD during the cat critical period trigger rapid remodeling of thalamocortical circuits in primary visual cortex in favor of the open eye. A related form of synaptic plasticity, elicited by opening the previously closed eye and closing the previously open eye (reverse-MD) can produce recovery of cortical function. We will first determine the contribution of each sleep state to the cortical plasticity elicited by MD. We will then determine if the effects of sleep on cortical plasticity are mediated by the patterns of neural activity present in REM or nonREM sleep. We will then investigate the role of sleep in the cortical plasticity elicited by reverse-MD.